Crustaceans vs. Molluscs

The major difference between both of these vertebrates is their group from which they belong to. This is the Crustaceans which belong to the phylum that is known as the Arthropoda. In contrast, the mollusks themselves are considered as a major phylum. The Crustaceans are belonging to those vertebrates who have chitinous exoskeleton. On the other side, you can easily find the presence of the calcareous shells in some of the mollusks. If you find a crustacean, then you will b amazed to discover that it can be classified as one of the more than 40,000 species of animals that come under the phylum Crustacea. A mollusk is any of the more than 50,000 species of animals which are come under the phylum of Mollusca. In most of the mollusks, you will find three main body regions. First one is known as the head which storing the sensory organs along with the “brain”. The second major part is called visceral mass containing the internal organs. A muscular “foot” is the third major part. In majority of the mollusks, you will find shells, but not every mollusk has shell which is quite venerable to being squished. In the case of the Crustaceans, you will locate a clearly segmented body that is well furnished with three distinct segments. The first one is the head while the second and third are the thorax and abdomen. Every crustacean is well protected with a hard, protective exoskeleton that is made of chitin. The color, size and shape of this exoskeleton can vary in their various species.


The nature of the Crustacean is class that comes into the phylum of Arthropoda. The presence of the jointed appendages, chitinous exoskeleton that is tough in nature, compound eyes, and endocrine system are the unique features of the Arthropods. The body shape of the crustaceans has two prominent parts known as the abdomen and the cephalothorax that is comprised of the cephalon and thorax. In order to close the cephalothorax, the shield-like carapaceen is present. The Crustaceans are well equipped with three pairs of appendages that act as the mouth parts, two pairs of antennae, and several pairs of legs which make them easy to survive. In some of their species, the numbers of leg pairs vary. These are the two pairs of antennae that you will never find in other arthropods. Every crustacean is largely aquatic and you are able to discover it in both marine and freshwater habitats. The best examples of the Marine crustaceans are crabs, shrimps, lobsters and barnacles. Some of the crayfish, crabs and copepods are known to be the freshwater crustaceans.


This is the Phylum Molluscs that is known to be the second largest extremely diverse group. The Molluscs have the capability of bearing the difficulties of various sorts of environments easily and effectively. This is the major reason that you can discover them in various types of environments which consist of both the aquatic and terrestrial ecosystems. The snails, slugs, scallops, clams, octopuses, cuttlefish, oysters, and lots of others are come under the head of the Molluscs. The Molluscs can be found in different body sizes starting from the microscopic size to huge ones. The presence of some of the mollusks is very useful for human diet because some of them such as the oysters, clams, scallops, muscles, octopuses, and squids are considered as the important food sources of humans. Every Mollusc except the cephalopods has the muscular foot which acts as the organ of locomotion, attachment, food capture, digging and lots of other functions. A visceral mass is responsible for providing the digestive and reproductive organs in every Mollusc.

Key Differences between Crustaceans and Molluscs

  1. The Crustaceans come under the well famous phylum of the Arthropoda. The Molluscs are thought to be one of the major phyla.
  2. The Crustaceans are protected by the chitinous exoskeleton. For the protection purpose, some of the Molluscs have the calcareous shells.
  3. The crustacean exhibits segmented biramous appendages which is not the feature in the Molluscs.
  4. Unlike the Molluscs, the body of the animals come under the crustaceans is divided into two parts which are called the cephalothorax and abdomen.
  5. The muscular foot is the main feature of the Molluscs for performing various activities not present in the crustaceans.
  6. The numbers of species are different in both the Mollusca and the Crustaceans.

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